Binocular Vision

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Middle School




   Jelly Beans
   Cup for Jelly Beans
   Papers with 2 spots in appropriate locations (for blind spot demo)
   Paper towel tubes (they are decorated with lots of colored tape)
   Senses poster 

Safety Precautions

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. Don’t let anyone choke on the jelly beans.


Put the jelly beans in the cups. Photo copies of the blind spot card should be made for each participant. Also it is useful to have a large version of the eye anatomy to use when presenting this demo.


For the see through hand demo, participants are given one eyeball separator tube and then they are instructed to:

• Hold the tube in their right hand, and place it against the side of their left hand.

• Look through the tube with their right eye

This will give the illusion that they are looking through a hole in their left hand!

For the separate eyeballs demo, participants are given two tubes, and instructed to hold one up against each eye (glasses must be removed to do this). Then have them perform the following tasks:

Move one tube up and the other down, and describe what they see. Repeat for side to side. Bring the tubes together until they see only one circle (this is binocular vision).

What To Say

Alright, now I am going to show you how to see a hole in your hand. First, everyone needs to take a tube and put it up to one eye. Hold the tube right next to your face and put your hand near your face. Now put your other hand next to the tube, closer to the end and look through both eyes – you can see a hole in your hand!! So, why do you think this happens?? Well, when you see something, the brain takes images from both eyes and combines them together to form the image that you see. In this demo, your brain is getting a different image from each eye and when it puts them together, it looks like you have a hole in your hand!!

Why It Is

In normal life, your vision is unobstructed and you view the world using both eyes, each looking in the same direction. As a result, your brain receives essentially the same image from both eyes at the same time. This type of vision is called binocular vision and it is very important for depth perception. In these demonstrations, binocular vision is disrupted by placing a tube over one or both eyes. Your brain is then receiving tow different images simultaneously, resulting in the illusions. A similar illusion occurs when you cross your eyes.

Real Life Examples

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